Final Report on APMP.T-K7 Key Comparison of water triple point cells Shu-Fei Tsai1, Rod White2, Jun Tamba3, Kazuaki Yamazawa3, Mong-Kim Ho4, C M Tsui5, Ghufron Zaid6, Aditya Achmadi6, Kee Sool Gam7, Hafidzah Othman8, Nurulaini Md Ali8, Kho Hao Yuan9 (Before Sep 2011), Ye Shaochun9 (Since Nov 2011), Hans Liedberg10, Charuayrat Yaokulbodee11 1Center for Measurement Standards, ITRI (CMS/ITRI), Taiwan 2Measurement Standards Laboratory(MSL), New Zealand 3National Metrology Institute of Japan, AIST (NMIJ/AIST), Japan 4National Measurement Institute of Australia (NMIA), Australia 5Standards and Calibration Laboratory (SCL), Hong Kong 6Puslitbang KIM-LIPI, Indonesia 7Korea Research Institute of Standards and Science (KRISS), Korea 8National Metrology Laboratory, SIRIM Berhad (SIRIM), Malaysia 9National Metrology Center (NMC), A*STAR, Singapore 10National Metrology Institute of South Africa (NMISA), South Africa 11National Institute of Metrology Thailand (NIMT), Thailand Pilot Laboratory: CMS, 1Center for Measurement Standards, ITRI (CMS/ITRI), Taiwan Co-Pilot Laboratories: MSL, 2Measurement Standards Laboratory of New Zealand, New Zealand NMIJ, 3National Metrology Institute of Japan, AIST (NMIJ/AIST), Japan 1/92 Table of Contents 1. Introduction 3 2. Organization of the comparison 3 2.1 Participants 3 2.2 Method of the comparison 3 2.3 Transfer cells and two CMS reference cells 4 2.4 Laboratory equipment and uncertainty 4 3. Comparison of the transfer cells at CMS 4 3.1 Experimental setup 4 3.2 Measurement procedure 7 3.3 Data analysis method 7 4. Measurements of TPW cells at CMS 8 4.1 Stability of two common reference cells 8 4.2 Temperature differences between transfer cells and reference cells 10 4.3 Uncertainty budget 12 5 Temperature difference between the national reference and the APMP.T-K7 14 reference cells in pilot laboratory 6. Temperature difference between the transfer cells and the national reference 15 7. Comparison of the national reference 18 7.1 Temperature difference between the national reference and the APMP reference 18 7.2 APMP.T-K7 reference value 19 7.3 Linking APMP.T-K7 to CCT-K7 21 8. Bilateral equivalence 24 Reference 25 Appendix 1 Measurement report form for APMP.T-K7 26 Appendix 2 Comparison of the national reference against APMP.T-K7 reference 34 by the pilot Appendix 3 Calibration of the transfer cell against national reference by the 40 participant Appendix 4 Immersion Profile 76 Appendix 5 Comparison of the transfer cell against national reference before 87 sending to and back from CMS Appendix 6 Additional explanation 88 2/92 1. Introduction This is the report of APMP.T-K7 key comparison of water-triple-point cells. The decision to organize this comparison was made at the APMP-TCT meeting in November 2000, but was postponed until the final report of CCT-K7 was published in 2006. CMS (Taiwan) organized the comparison, with the support from co-pilot institutes MSL (New Zealand) and NMIJ (Japan). The final version of the protocol was submitted to CCT WG7 in May 2007 and obtained approval in October 2007. The comparison measurements were commenced in February 2008 and finalized in September 2009, and the report submission was closed on 23 Nov. 2010, however the closure measurement results, after cells were back to each laboratory, from some participants were not collected in full until January 2011. 2. Organization of the comparison 2.1 Participants A total of 11 NMIs took part in this comparison as shown in the following table: Table 1: Participants of APMP.T-K7 Country NMI Contact Person Email National Measurement Institute, Ms. Kim Nguyen Kim.Nguyen@measurement. Australia Australia (NMIA) gov.au Standards and Calibration Mr. C M Tsui [email protected] Hong Kong Laboratory(SCL) Ms. Julian Cheung [email protected] Mr. Aditya Achmadi [email protected] Indonesia Puslitbang KIM-LIPI Dr. Ghufron Zaid [email protected] National Metrology Institute of + Dr. Jun Tamba [email protected] Japan Japan(NMIJ/AIST) Korea Research Institute of Standards Korea Dr. Kee Sool Gam [email protected] and Science(KRISS) Standards & Industrial Research Ms. Hafidzah Othman [email protected] Malaysia Institute of Malaysia(SIRIM)Berhad Ms. Nurulaini Md Ali [email protected] Measurement Standards New Zealand+ Dr. Rod White [email protected] Laboratory(MSL) [email protected] Mr. Kho Hao Yuan Singapore National Metrology Centre(NMC) star.edu.sg Dr. Wang Li since Sept. [email protected] National Metrology Institute of South South Africa Mr Hans Liedberg [email protected] Africa (NMISA) Center for Measurement * Ms. Shu-Fei Tsai [email protected] Taiwan Standards(CMS)/ITRI National Institute of Metrology Ms.Charuayrat Thailand [email protected] Thailand(NIMT) Yaokulbodee *: Pilot Laboratory +: Co-Pilot Laboratories 2.2 Method of the comparison The comparison was organized as a collapsed star comparison and consisted of four phases: 3/92 1) CMS completes the comparison of its national reference against the two common reference cells and sends the report to two co-pilots before the inter-cell comparison begins; 2) each participating laboratory selects one of its cells for use as a transfer cell and directly compares it against its national reference; 3) the selected transfer cell is sent together with the measurement results to CMS where all transfer cells are compared against two common reference cells; 4) the transfer cells are sent back to the laboratories to directly re-compare with the same reference cell(s), as before, to check the transfer cell stability. The participants were asked to compare the selected transfer cell against their national reference on two separately prepared ice mantles. Measurements should not start until at least one week after the preparation of the ice mantle, and then be carried out in about two weeks, resulting in a minimum of ten results per mantle. The protocol recommended that the ice mantle of the transfer cell be prepared by using the BIPM technique, and the measurement procedure should be that normally applied by the laboratory. The participants were also asked to measure an immersion profile. At CMS, all cells were compared with two common reference cells provided by CMS. The mean of the temperature difference between the transfer cell and these two reference cells measured on the same day served the comparison result for all participants' cells. For each cell, measurements were made at least for two different mantles. Immersion profiles were also measured at CMS. 2.3 Transfer cells and two CMS reference cells The transfer cells selected by each participant and the two CMS reference cells are presented in Table 2. The designations used in this report differ in many cases from those used by the laboratories because a uniform labeling system was adopted here for convenience. Each cell is designated here by the acronym of the laboratory owning the cell, followed by a serial number. The sixth column of the table lists special accessories which were sent with some of the cells and which were also used for the measurements at CMS. 2.4 Laboratory equipment and uncertainty The equipment, measuring conditions, and ice mantle preparation technique are summarized in Table 3. The detailed uncertainty budget and immersion profile of cell submitted by each participating laboratory are reported in Table 3 and Appendix 2-4. 3. Comparison of the transfer cells at CMS 3.1 Experimental setup The water triple point cells were kept in one TPW maintenance bath, which can maintain up to four cells. The set-point of the bath was 1 mK below the triple point. All measurements were made with the same 25.5 Ω SPRT. An ASL F900 bridge measured the resistance of the thermometer against a 100 Ω standard resistor, which was kept in an oil bath regulated at 20 °C. The oil bath was equipped with a resistance thermometer to monitor the temperature. The ASL Bridge was connected to a computer via an IEEE interface to remotely control the instrument settings and data acquisition. The bridge settings for the bandwidth, gain, and carrier frequency were 0.1 Hz, 105, and 30 Hz respectively. Twelve measurements, taken every 33 seconds at currents of both 1 mA and 2 mA, were used to extrapolate and 4/92 determine the zero-current resistance. The laboratory temperature was controlled to be within (23±2) °C. 5/92 Table 2: Transfer cells selected by the participating laboratory and reference cells of CMS Cell Year of Accessories or Depth of well designation Manufacturer Inner diameter Cell diameter Country Laboratory Model of cell fabrication or comments on below water used in this or type of well /mm /mm purchase special use surface / mm report CMS5029 Taiwan CMS Hart Scientific 5901A-Q 2008 — 12 50 265 CMS5030 Australia NMIA NMIA AC6 NMIA 1971 — 50 227 Hong Kong SCL SCL5045 Hart Scientific 5901A-G 2007 — 12 50 291 Indonesia KIM-LIPI KIM-LIPI224 PTB 5 PTB 89 1989 — 12 50 215 Centering adjuster / Japan NMIJ NMIJT93-3 TOA KEIKI SY-12 1993 12 65 238 Height adjuster / Clip Aluminum Korea KRISS KRISS2000-24 KRISS 2002 11 50 246 bushing used CRM 51-01- Malaysia SIRIM SIRIM2000-22 KRISS 2007 — 11 50 246 001 New MSL MSL01-02 MSL 2001 — 9 60 248 Zealand Singapore NMC NMC2087 Jarrett B11 2003 — 11 64 285 Foam pad at South Africa NMISA NMISA1181 Hart Scientific 5901A-G 2004 12 50 265 bottom of well Thailand NIMT NIMT1480 Hart Scientific 5901 2005 — 13.6 60 265 6/92 Table 3: Overview of the equipment and measuring conditions used in each participating laboratory Measurement Repeated Temp. Storage Technique ice